How to hide a baby bump?

any good ideas on how to hide a baby bump? before i say anything else im just saying im not pregnant, but im working on a story where my main character is pregnant, and trying to hide it from her fiance. the deal is she weighs like 115-120 pounds is about 5 foot 9 and pregnant. she has to hide this from her fiance for 4 months, but how? they live together and she loves her short short and cami's. like i said she needs to hide it but i don't have a clue. because they love to cuddle, get all touchy feely, but how can they still be like that and him not know she's pregnant? any help, advice, ETC would be great, thanks!